1. Field of the Invention
The present invention relates to an engine warming-up apparatus for a vehicle to warm up an internal combustion engine in utilizing a high temperature coolant heat-accumulated within a heat insulating device disposed in an engine coolant circuit. More particularly, the present invention relates to an engine warming-up apparatus having an improved degassing function performed in the heat insulating device.
2. Description of Related Art
A cooling system used for a water-cooled engine has been mounted on various vehicles to cool the engine at a proper temperature. FIG. 14 shows such a conventional cooling system 100 mounted on a vehicle to cool an internal combustion engine 101. In the vehicle, heat released from the engine 101 is utilized for heating the passenger compartment. The cooling system 100 includes, such as, a radiator 103, a thermostatic control valve 104, and a heater core 105, which are connected between the engine 101 and a water pump 102 in forming respective closed loops. A completely closed reserve tank, or degassing tank, 107 is coupled to an upper tank 106 of the radiator 103, whose lower tank 108 is connected to a thermostat 109. The internal pressure in the engine cooling system 100 is set at a predetermined value by a pressure cap 110 attached to the reserve tank 107.
A pressure circuit 111 connects the reserve tank 107 to the inlet of the water pump 102 to apply a uniform pressure onto respective pertinent portions of the engine 101. A degassing circuit 112 communicates the upper tank 106 of the radiator 103 with the reserve tank 107 to degas the coolant. The thermostat 109 communicates with the inlet of the water pump 102 through a suction pipe 113. The coolant of engine 101 bypasses the radiator 103 through a bypass pipe 114 at low temperature. In the cooling system for the engine 101 equipped with the completely closed reserve tank 107, rubber hoses 121 are used as shown in FIG. 15 to communicate the coolant between the radiator 103 and the reserve tank 107, between the engine 101 and the reserve tank 107, and between the reserve tank 107 and the inlet of the water pump 102. The hoses 121 are secured using binding members 122 and 123, such as hose bands or the like, to the respective above portions.
With the cooling system 100 as described above, when the water-cooled engine 101 is restarted after made inoperative for a long time, and particularly during winter time when the outside temperature is low, the engine 101 needs a warming up operation for a certain period. As a result, there raise problems that such a warming up operation grossly increases the fuel consumption, brings economic disadvantages, and impairs the drive performance of the vehicles until the engine reaches a suitable temperature.
To solve such problems, some prior arts have been proposed as disclosed in JP-A-58-133415 and JP-U-2-92054. In an engine warming-up apparatus for a vehicle disclosed in JP-A-58-133415, a heat insulating tank storable of the almost whole volume of the coolant in the cooling circulation is provided to supply to the engine a high temperature coolant within the heat insulating tank at a time of the engine start to warm up the engine. In an engine warming-up apparatus for a vehicle JP-U-2-92054, an accumulator for warming up the engine, which is connected to the engine and the radiator through pipes, is arranged to exchange the coolant in the accumulator with the coolant on the engine side according to the temperature difference given from temperature sensors attached to the accumulator and the engine (or radiator), respectively.
The prior art disclosed in JP-A-58-133415, however, needs to open an electromagnetic valve placed in a coolant passage when a high temperature coolant in the heat insulating device is to be supplied to the engine. Such construction makes the cost extremely higher since a controller for opening and closing the electromagnetic valve is required. Moreover, the temperature of the coolant within the heat insulating device tends to be lowered more or less, so that a portion of the coolant, having a low temperature, may fall downward and gather together at a bottom of the heat insulating device. The above prior art has an insulator outlet opened around the lower portion of the insulator. As a result, when the coolant within the reserve tank is supplied to the engine, the coolant at a relatively low temperature is first supplied, thereby deteriorating the warming-up function of the system. Furthermore, the reserve tank has a large volume which can accumulates almost the whole amount of the coolant in the cooling circuit, and such a reserve tank requiring a large content becomes more difficult to be mounted in the engine compartment of vehicles such as automobiles, because the engine compartment tends to be denser these days.
The prior art disclosed in JP-U-2-92054, as well as the prior art in JP-A-58-133415, needs to open the valve when the high temperature coolant stored in the accumulator is supplied to the engine, so that the system requires a controller to open and shut the valve, which leads to extremely high costs. The accumulator is not provided with a degassing passage in the accumulator. Therefore, air is unavoidably trapped at the top of the accumulator when the coolant is poured in the accumulator, so that there raises a problem that the coolant cannot be filled in the whole volume of the heat insulating device.